Reading the book, it's pretty clear that in a lot of the ways, the Trisolarians are stand-ins for the Americans; increasingly so now that America has pretty much explicitly stated they would like to halt Chinese scientific progress, at least in select areas.
You flatter Americans far too much, most Chinese consider them politically misguided equals at best, at worse, ignorant people who should stay far from Asia.
It is to me more obvious that Trisolaris represents a long term whole of earth threat, such as the climate crisis. The theme of different solutions (run away from solar system, stay and fortify, colonise inside the solar system) are themes that Liu Cixin has in many different works, all as answers to a sort of societal crisis. He then explores the themes and ideas of each idea, and the effort needed for humanity to succeed.
The message is that when we work hard and are creative in our solutions, there is no obstacle we cannot overcome. And the American solution (to lay down and just let climate change happen, then let the rich hide away while the poor are culled) is satirized as especially bad, when the first thing that happens when humanity has to move to Australia is that the rich get killed by the rabble, which I assume is what the author thinks would happen to all those oligarchs once they retreat to their elevated tropical islands.
Americans are allegorized in Three Body problem as themselves.